bundle with the newest released bundler

amatsuda · amatsuda · commit 79884cdf5ae2 · 2017-01-11T17:30:43.000+09:00
to avoid old bundler bug that tries to bundle beta gems
diff --git a/.travis.yml b/.travis.yml
@@ -1,6 +1,7 @@
 language: ruby
 sudo: false
 cache: bundler
+before_install: gem update bundler --no-document
 rvm:
   - 1.9.3
   - 2.0.0
